For me, it's existence and personal meaning.
Already, everyone's a somebody because we're existing or have existed within the universe. It's big, infinite, always expanding, and has no conscious. And yet, it picked us, those who are now or was now, to exist in within it. Already, we're somebodies, at least to the universe.
Now...personal meaning is the second part of it. Sure, we physically exist, but what does it mean to exist -- to have meaning? To have purpose? Personal meaning is just that, and it's what mostly everyone in here has stated -- it's what your existence means to you.
To me, being "somebody" means to live life to the fullest. To embrace my flaws and my strengths, and see that I improve as I grow older. My "self" is loving the people I care deeply about and diving into the things that make me passionate. My meaning of "somebody" doesn't apply social standards all that much.
But to others, it does. Being "somebody" to someone else can mean making that big money, having that family, carrying a legacy where everyone knows you.
And that's cool too. What we see in "somebody" stems from how society, our circles, and how our experiences have affected us. There's no clear answer, nor a correct answer, to this.
Just...I guess, in the grand scheme of things, we are all "somebody" because the universe made us all "somebody" (whether we're living now, having passed away, or about to be born). We're all unique in our lives, our decisions, and our perspective. Maybe it's a cop-out answer, but for me, it kinda holds a strong meaning.